Biochar can be defined simply as properly produced char (charcoal) used for agricultural purposes. It can be produced from any type of biomass, including agricultural and forestry waste streams and manure. Biochar is manufactured by heating the biomass feedstock in an oxygen deprived environment, a process which is called "pyrolysis". Syngas, a flammable combination of hydrogen, carbon monoxide and methane, and excess heat are byproducts of the pyrolysis process. Once the reaction is started, it is largely self-sustaining, requiring no additional input of energy.

Once it is produced, biochar is spread on agricultural fields and incorporated into the top layer of soil. Biochar has many agricultural benefits. It increases crop yields, sometimes substantially if the soil is in poor condition. It helps to prevent fertilizer runoff and leeching, allowing the use of less fertilizers and diminishing agricultural pollution to the surrounding environment. And it retains moisture, helping plants through periods of drought more easily. Most importantly, it replenishes exhausted or marginal soils with organic carbon and fosters the growth of soil microbes essential for nutrient absorption, particularly mycorrhizal fungi.

Studies have indicated that the carbon in biochar remains stable for millenia, providing a simple, sustainable means to sequester historic carbon emissions that is technologically feasible in developed or developing countries alike. The syngas and excess heat can be used directly or employed to produce a variety of biofuels.

When biochar is created from biomass, approximately 50% of the carbon that the plants absorbed as CO2 from the atmosphere is "fixed" in the charcoal. As a material, the carbon in charcoal is largely inert, showing a relative lack of reactivity both chemically and biologically, and so it is strongly resistant to decomposition. Hence, biochar effectively recycles carbon from the atmosphere back to the soil in form that is at least an order of magnitude more stable than the organic material it was created from.

Of the many organic and inorganic substances that contain carbon atoms, only diamonds could potentially provide a more permanent carbon store than charcoal. Hence, biochar offers us a golden opportunity to remove excess CO2 from the atmosphere and sequester it in a virtually permanent and environmentally beneficial way.

Effect of Biochar on Soil Fertility

Below are a series of photos illustrating the effect of biochar on soil fertility. A vast majority of biochar trials to date show positive results such as these. They were taken during the International Biochar Initiative Conference held in Terrigal, Australia from April 29 to May 2, 2007.

The test plots shown in the photographs compare the following after 10 weeks:

Biochar with NPK fertilizer compared to NPK fertilizer alone. The capacity of biochar to help plants absorb nutrients is clearly evident in this photo.

Biochar without fertilizer compared with plain soil. Again, the ability of biochar to help plants absorb whatever nutrients are available in soil is evident in this photo.

Biochar only compared with NPK fertilizer only. This photo demonstrates that biochar may provide a means produce comparable results to conventional agriculture practice in organic farming or with reduced NPK usage.

Scientific Research on Biochar

Biochar has been the focus of a significant body of scientific research to date, and the number and scope of research projects is rapidly expanding. There are several resources currently available on the Internet related to scientific papers and research which are listed below.

International Biochar Initiative Bibliography

The International Biochar Initiative maintains a comprehensive listing of most scientific papers related to biochar. Go

Johannes Lehmann

Johannes Lehmann, an associate professor of Cornell University's Department of Crop and Soil Sciences, is one of the principal researchers working on biochar. Listed on his website are the biochar-related publications he has contributed to. Go